Enzyme-linked immunosorbent assay of nicotine metabolites

A diverse paper sensor for the rapid determination of nicotine and cotinine traces in air, vaping liquid, and human saliva

The smoking of nicotine and passive exposure to environmental tobacco smoke can lead to many chronic medical conditions such as respiratory, cardiovascular, and cancer diseases. Nicotine smoking can also cause complications for patients undergoing medical procedures. The prevalence of vaping among young people has added a significant challenge to the health care systems as many commercial vaping oils contain undeclared nicotine content, thus leading to nicotine addiction. Governments around the world criminalised the undeclared presence of nicotine in vaping oils. Therefore, there a is strong demand for new materials and sensors that can rapidly detect nicotine/tobacco smoke in vaping products and the environment. Similarly, there is an ongoing need for rapid methods to determine the concentration of the nicotine metabolite, cotinine, in patients prior to medical procedures. To address these needs, we have synthesised and utilised a cost-effective paper sensor for the rapid screening of nicotine and cotinine in vaping the oil, the gas phase, and the human saliva by surface-enhanced Raman spectroscopy (SERS). The new sensor can detect ultra traces of nicotine and cotinine down to 1 pg/mL and 1 ng/mL respectively, within 20 min. The new sensor can be recycled for repeated screening of nicotine and its metabolite, thus maximizing its economic viability. The was successfully utilised for the detection of nicotine in tobacco smoke and in spiked human saliva by a handheld Raman spectrometer, thus indicating its potential for real-life applications.

Survey of Secondhand Smoke for 3-Year-Old Children in the Current Era of New Tobacco Products

AIM

To investigate children's exposure to secondhand smoke and aerosols in the current era of new tobacco products.

METHODS

A total of 200 children were recruited from among children who had undergone health checkups for 3-year-olds at the clinic. We investigated the smoking status of their families using a questionnaire and measured urinary cotinine concentrations in their children. The children were divided into four groups based on their families' smoking status: no smokers (n = 114), exclusive combustion cigarette smokers (n = 35), both combustion cigarette and heated tobacco product smokers (n = 12) and exclusive heated tobacco product smokers (n = 39).

RESULTS

Of the 200 children, 53 (26.5%) had detectable urinary cotinine levels. Of these, 12 (6.0%) were classified as having heavy exposure to secondhand smoke (urinary cotinine concentration ≥ 5 ng/mL). Urinary cotinine concentrations among children living with exclusive heated tobacco product smokers were significantly lower than those among children living with exclusive combustion cigarette smokers, but higher than those in children whose family members did not smoke at all. Relative to exclusive combustion cigarette smokers, exclusive heated tobacco product smokers were significantly more likely to smoke indoors.

CONCLUSIONS

Secondhand aerosol exposure from heated tobacco products may be reduced but cannot be completely eliminated.

Simultaneous Determination of Tobacco Smoke Exposure and Stress Biomarkers in Saliva Using In-Tube SPME and LC-MS/MS for the Analysis of the Association between Passive Smoking and Stress

Passive smoking from environmental tobacco smoke not only increases the risk of lung cancer and cardiovascular disease but may also be a stressor triggering neuropsychiatric and other disorders. To prevent these diseases, understanding the relationship between passive smoking and stress is vital. In this study, we developed a simple and sensitive method to simultaneously measure nicotine (Nic) and cotinine (Cot) as tobacco smoke exposure biomarkers, and cortisol (CRT), serotonin (5-HT), melatonin (MEL), dopamine (DA), and oxytocin (OXT) as stress-related biomarkers. These were extracted and concentrated from saliva by in-tube solid-phase microextraction (IT-SPME) using a Supel-Q PLOT capillary as the extraction device, then separated and detected within 6 min by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using a Kinetex Biphenyl column (Phenomenex Inc., Torrance, CA, USA). Limits of detection (S/N = 3) for Nic, Cot, CRT, 5-HT, MEL, DA, and OXT were 0.22, 0.12, 0.78, 0.39, 0.45, 1.4, and 3.7 pg mL-1, respectively, with linearity of calibration curves in the range of 0.01-25 ng mL-1 using stable isotope-labeled internal standards. Intra- and inter-day reproducibilities were under 7.9% and 14.6% (n = 5) relative standard deviations, and compound recoveries in spiked saliva samples ranged from 82.1 to 106.6%. In thirty nonsmokers, Nic contents positively correlated with CRT contents (R2 = 0.5264, n = 30), while no significant correlation was found with other biomarkers. The standard deviation of intervals between normal beats as the standard measure of heart rate variability analysis negatively correlated with CRT contents (R2 = 0.5041, n = 30). After passive smoke exposure, Nic levels transiently increased, Cot and CRT levels rose over time, and 5-HT, DA, and OXT levels decreased. These results indicate tobacco smoke exposure acts as a stressor in nonsmokers.

Salivary Carbohydrate-Deficient Transferrin in Alcohol- and Nicotine-Dependent Males

Serum carbohydrate-deficient transferrin (CDT), an 80 kDa glycoprotein, is one of the most commonly employed biomarkers to detect alcohol dependence. Some salivary glycoproteins such as α-amylase, clusterin, haptoglobin, light/heavy-chain immunoglobulin, and transferrin, which alter glycosylation in alcohol-dependent persons, have been suggested to be potential alcohol markers. However, their identification is based on indirect analysis of lectin glycosidic bonds and molecular weight. We investigated the CDT content in the saliva of alcohol- and nicotine-dependent men. The CDT concentration (ng/mL, ng/mg protein) was determined by an Enzyme-Linked Immunosorbent Assay (ELISA) commercial kit in 55 men: 20 healthy social drinkers (C), 10 chronic cigarette smokers (S), 10 alcohol-dependent non-smokers (A), and 15 alcohol-dependent smokers (AS). Surprisingly, there were no differences in the concentrations of CDT between the studied groups. Salivary pH was the lowest in the AS and the highest in the A group. Therefore, salivary CDT cannot be used as an alcohol dependence marker as measured by ELISA. We suggest that direct identification of glycoproteins is necessary to search for potential salivary alcohol biomarkers. Molecules smaller than 40 kDa, which easily translocate from blood to the saliva, might be preferred as salivary alcohol markers.

Urinary Cotinine as a Biomarker of Cigarette Smoke Exposure: A Method to Differentiate Among Active, Second-Hand, and Non-Smoker Circumstances

Objective:

To review the literature on the use of urinary cotinine as a biological marker of cigarette smoke exposure.

Methods:

Narrative review of original and review articles on the topic of interest, published in Portuguese or English by June 2018, and selected in the following online databases: PubMed and Virtual Health Library (VHL).

Results:

Urinary cotinine is usually the recommended biomarker to estimate exposure to cigarette smoke, and can be used alone or, preferably, in association with questionnaires. Different analytical techniques can be used to quantify urinary cotinine and are differently performed because of urine sample interfering factors.

Conclusion:

The precise classification of smoking status is essential. It is advisable to use objective measurements regarding smoking habits since self-reported smoking may not always represent the true smoking status of the individual, particularly in groups that are more vulnerable to omitting the information of questionnaries, in addition, it has possible biases of memory. The accurate assessment of smoking is crucial to improve clinical management and counseling for different diseases as well as the establishment of preventive strategies. So, the use of urinary cotinine as a biomarker of cigarette smoke exposure seems to be a suitable assay to distinguish non-smokers from passive and active smokers.

Busgang S, Matt GE. Comparison of Liquid Chromatography Mass Spectrometry and Enzyme-Linked Immunosorbent Assay Methods to Measure Salivary Cotinine Levels in Ill Children

Objective: Cotinine is the preferred biomarker to validate levels of tobacco smoke exposure (TSE) in children. Compared to enzyme-linked immunosorbent assay methods (ELISA) for quantifying cotinine in saliva, the use of liquid chromatography tandem mass spectrometry (LC-MS/MS) has higher sensitivity and specificity to measure very low levels of TSE. We sought to compare LC-MS/MS and ELISA measures of cotinine in saliva samples from children overall and the associations of these measures with demographics and TSE patterns. Method: Participants were nonsmoking children (N = 218; age mean (SD) = 6.1 (5.1) years) presenting to a pediatric emergency department. Saliva samples were analyzed for cotinine using both LC-MS/MS and ELISA. Limit of quantitation (LOQ) for LC-MS/MS and ELISA was 0.1 ng/ml and 0.15 ng/ml, respectively. Results: Intraclass correlations (ICC) across methods = 0.884 and was consistent in sex and age subgroups. The geometric mean (GeoM) of LC-MS/MS = 4.1 (range: < LOQ - 382 ng/mL; 3% < LOQ) which was lower (p < 0.0001) than the ELISA GeoM = 5.7 (range: < LOQ - 364 ng/mL; 5% < LOQ). Similar associations of cotinine concentrations with age ( < -0.10, p < 0.0001), demographic characteristics (e.g., income), and number of cigarettes smoked by caregiver ( > 0.07, p < 0.0001) were found regardless of cotinine detection method; however, cotinine associations with sex and race/ethnicity were only found to be significant in models using LC-MS/MS-derived cotinine. Conclusions: Utilizing LC-MS/MS-based cotinine, associations of cotinine with sex and race/ethnicity of child were revealed that were not detectable using ELISA-based cotinine, demonstrating the benefits of utilizing the more sensitive LC-MS/MS assay for cotinine measurement when detecting low levels of TSE in children.

Assessment of cotinine in urine and saliva of smokers, passive smokers, and nonsmokers: Method validation using liquid chromatography and mass spectrometry

BACKGROUND

Self-report does not provide complete information about tobacco smoke exposure among users and is not relevant for secondhand exposure detection. Biochemical screening for primary metabolite of nicotine would be useful to validate the smoking status and exposure to secondhand smoke.

AIMS AND OBJECTIVES

This study was designed to evaluate the performance of a sensitive and rapid method to verify smoking status among smokers, passive smokers, and nonsmokers by quantification of cotinine in saliva and urine using liquid chromatography and mass spectrometry.

MATERIALS AND METHODS

Cotinine (urine and saliva) levels were measured in 98 participants out of which active users (smoked tobacco users; n = 56) and persons exposed to tobacco smoke (passive smokers; n = 15). Values obtained were compared with nonusers (nonsmokers; n = 27). A simple, rapid, and sensitive method was developed and validated for this purpose. With minimal sample preparation, the current analytical procedure showed a wide detection range (1.1-1000 ng/mL) which made it suitable for analyzing various biological matrices.

RESULTS

The mean cotinine levels of urine for smokers, passive smokers, and nonsmokers were 1043.7, 36.63, and 13.6 ng/ml, respectively, while in saliva, it was 327.39, 18.31, and 9.53 ng/ml, respectively.

CONCLUSION

Analysis of variance showed that cotinine levels (urine and saliva) of smokers were significantly higher levels than passive smokers and nonsmokers (P < 0.01). Similarly, passive smokers also had significantly higher cotinine levels (urine and saliva) than nonsmokers (P < 0.001).

Clinical and radiographic periodontal status and whole salivary cotinine, IL-1β and IL-6 levels in cigarette- and waterpipe-smokers and E-cig users

The aim was to compare the clinical (plaque index [PI], bleeding on probing [BOP], probing pocket depth [PPD] and clinical attachment loss [CAL]) and radiographic (marginal bone loss [MBL]) periodontal parameters and whole salivary cotinine, interleukin (IL)-1β and IL-6 levels among cigarette-smokers, waterpipe-smokers, E-cig users and never-smokers. In total, 154 male individuals (39 cigarette-smokers, 40 waterpipe-smokers, 37 E-cig users and 38 never-smokers) were included. Full mouth PI, BOP, PPD and CAL were measured on all teeth (excluding third molars); and MBL was measured in digital intra-oral radiographs. Unstimulated whole salivary flow rate (UWSFR) and whole salivary cotinine, IL-1β and IL-6 levels were measured. Group comparisons were performed using one way analysis of variance and Bonferroni post-hoc tests. P-values less than 0.05 were considered statistically significant. There was no difference in UWSFR among the groups. Cotinine levels were significantly higher among cigarette- (P < 0.001) and waterpipe-smokers (P < 0.001) and E-cig users (P < 0.001) than never-smokers. IL-1β (P < 0.01) and IL-6 (P < 0.01) levels were significantly higher among cigarette- and waterpipe-smokers than E-cig users and never-smokers. There was no difference in PPD, CAL, mesial and distal MBL and whole salivary IL-1β and IL-6 levels among E-cig users and never-smokers. In conclusion, clinical and radiographic parameters of periodontal inflammation were poorer in cigarette and waterpipe smokers than E-cig users and never-smokers; and whole salivary cotinine levels were similar in all groups. Whole salivary IL-1β and IL-6 levels were higher in cigarette- and waterpipe-smokers than E-cig users and never-smokers.

Accuracy and utility of an epigenetic biomarker for smoking in populations with varying rates of false self-report

Better biomarkers to detect smoking are needed given the tremendous public health burden caused by smoking. Current biomarkers to detect smoking have significant limitations, notably a short half-life for detection and lack of sensitivity for light smokers. These limitations may be particularly problematic in populations with less accurate self-reporting. Prior epigenome-wide association studies indicate that methylation status at cg05575921, a CpG residue located in the aryl hydrocarbon receptor repressor (AHRR) gene, may be a robust indicator of smoking status in individuals with as little as half of a pack-year of smoking. In this study, we show that a novel droplet digital PCR assay for measuring methylation at cg05575921 can reliably detect smoking status, as confirmed by serum cotinine, in populations with different demographic characteristics, smoking histories, and rates of false-negative self-report of smoking behavior. Using logistic regression models, we show that obtaining maximum accuracy in predicting smoking status depends on appropriately weighting self-report and cg05575921 methylation according to the characteristics of the sample being tested. Furthermore, models using only cg05575921 methylation to predict smoking perform nearly as well as those also including self-report across populations. In conclusion, cg05575921 has significant potential as a clinical biomarker to detect smoking in populations with varying rates of accuracy in self-report of smoking behavior.

Screening for secondhand smoke in schoolchildren in Japan

BACKGROUND

There is no systematic screening for secondhand smoke exposure in children.

METHODS

In 2002, we began a secondhand smoke screening (SSS) program for grade 4 elementary schoolchildren with the cooperation of public administration. The SSS program consisted of urinary cotinine measurement in children and a questionnaire survey of their parents.

RESULTS

More than 1200 schoolchildren were enrolled in this program annually. The level of urinary cotinine in 30% of the children was >5 ng/mL, whereas in half of them it was undetectable. The major risk factor affecting cotinine level was mother's smoking. Average cotinine was significantly high in children who had a history of "short stature", "decayed tooth and/or periodontal disease," and "frequent stridor". In addition, the highest level of cotinine was detected in children whose father and/or mother smoked in the living room and the lowest level of cotinine was detected in children whose father and/or mother smoked on the veranda or outside the door. These levels, however, were two-fivefold higher than in children whose parents did not smoke. On follow-up questionnaire survey 4 years after initial SSS, significant elevated motivation for smoking cessation was noted.

CONCLUSIONS

The SSS program is a very simple mass screen that can be done using only a urine test and is very effective for motivating parents to stop smoking with regard to cost benefit.

Environmental tobacco exposure is associated with vaccine modified measles in junior high school students

Vaccine modified measles (VMM) affects individuals with attenuated vaccine induced immunity. An outbreak of measles occurred in a junior high school, starting from an unvaccinated eighth-grade student who developed natural measles and affected a majority of students who were immunized with a low potent strain of measles vaccine (TD97). To determine whether environmental tobacco smoke (ETS) exposure was associated with the development of VMM in this population, a questionnaire was used asking whether students had VMM symptoms during the outbreak and the smoking status of family members. VMM was defined in the study population as occurrence of fever and/or erythema, along with documented history of measles vaccination. A total of 513 students (85.9%) responded. Overall, the presence of in-house smokers did not differ between VMM students (49.3%) and non-VMM students (50.2%). However, in the ninth grade, presence of an in-house smoker was significantly higher in the family of VMM students (54.0%) than in non-VMM students (36.6%) (P = 0.044). Urinary cotinine levels were also measured in selected students (n = 37). Among families with at least one smoker, urinary cotinine levels were significantly higher in VMM students than in non-VMM students (P = 0.032). Furthermore, a multivariable logistic regression analysis showed that a high urinary cotinine level (>10 ng/mg creatinine; 13.5 percentile) was associated with the development of VMM. Our findings suggest that a high level of ETS exposure may be associated with an increased risk of VMM in a population with attenuated vaccine induced immunity against measles.

Estimation of cutoff values of cotinine in urine and saliva for pregnant women in Poland

Setting appropriate cutoff values and the use of a highly sensitive analytical method allow for correct classification of the smoking status. Urine-saliva pairs samples of pregnant women in the second and third trimester, and saliva only in the first trimester were collected. Offline SPE and LC-ESI-MS/MS method was developed in the broad concentration range (saliva 0.4-1000 ng/mL, urine 0.8-4000 ng/mL). The mean recoveries were 3.7 ± 7.6% for urine and 99.1 ± 2.6% for saliva. LOD for saliva was 0.12 ng/mL and for urine 0.05 ng/mL; LOQ was 0.4 ng/mL and 0.8 ng/mL, respectively. Intraday and interday precision equaled, respectively, 1.2% and 3.4% for urine, and 2.3% and 6.4% for saliva. There was a strong correlation between salivary cotinine and the uncorrected cotinine concentration in urine in the second and third trimesters of pregnancy. The cutoff values were established for saliva 12.9 ng/mL and urine 42.3 ng/mL or 53.1 μg/g creatinine with the ROC curve analysis. The developed analytical method was successfully applied to quantify cotinine, and a significant correlation between the urinary and salivary cotinine levels was found. The presented cut-off values for salivary and urinary cotinine ensure a categorization of the smoking status among pregnant women that is more accurate than self-reporting.

Simple and rapid assay method for simultaneous quantification of urinary nicotine and cotinine using micro-extraction by packed sorbent and gas chromatography-mass spectrometry

A simple and rapid method for determination of nicotine and cotinine levels in urine was developed using samples prepared by micro-extraction by packed sorbent (MEPS) and subjected to gas chromatography-mass spectrometry (GC-MS) analysis. This method provided good reproducibility, as well as good linearity of calibration curves in the range of 1-100 and 50-1000 ng/mL for quality control samples spiked with nicotine and cotinine, respectively. The detection limit of nicotine and cotinine was as low as 0.25 and 20 ng/mL, respectively. An evaporation procedure is not suitable for nicotine determination, thus an advantage of the present MEPS assay method is direct testing with GC-MS without the need for evaporation to a dry solvent. Our findings show that it may be useful for determining nicotine levels in various types of research studies.

Semipermeable membrane dressings can be used with the nicotine transdermal system and do not interfere with nicotine absorption

OBJECTIVE

Adverse skin reactions as a local side effect of nicotine patches sometimes interfere with smoking cessation therapy. We studied the effects of semipermeable membrane dressings (SMD) used under nicotine patches (NP) on nicotine absorption, as assessed according to the urinary cotinine levels, and skin symptoms.

METHODS

First, the urinary cotinine levels were compared in eight nonsmokers that applied NP over SMD and NP without SMD (Study 1). The urinary cotinine levels were measured using a highly sensitive competitive enzyme immunoassay. Second, 28 subjects undergoing NP therapy for diagnosed nicotine dependence were randomly assigned into two groups in a crossover design to receive NP over SMD and NP without SMD. The urinary cotinine levels and skin symptoms were compared between the two treatment groups. During the follow-up period of 48 weeks, the smoking cessation rate was evaluated (Study 2).

RESULTS

No statistical differences were observed in the urinary cotinine levels between the NP over SMD and NP without SMD groups. In Study 2, the skin symptoms improved with the use of SMD in 42.8% (6/14) of the patients and worsened in 28.5% (4/14) of the patients. No serious skin disorders were reported. The subjects followed in Study 2 exhibited smoking cessation rates of 92.8%, 78.5% and 64.2% at 12, 24 and 48 weeks, respectively.

CONCLUSION

The use of NP over SMD is a safe and effective alternative application to NP treatment for preventing the skin symptoms caused by NP without interfering with nicotine absorption.

Simultaneous measurement of urinary total nicotine and cotinine as biomarkers of active and passive smoking among Japanese individuals

OBJECTIVES

Measuring urinary cotinine is a popular and established method of biologically monitoring exposure to tobacco smoke. However, the lower detection limit of cotinine often impedes the evaluation of passive (second-hand) smoking and this, together with unconverted nicotine, does not reflect actual levels of exposure. Furthermore, a portion of the Japanese population might have decreased ability to metabolize nicotine. The present study was therefore carried out to validate the simultaneous analysis of total concentrations of free nicotine and cotinine and their glucuronides to determine actual levels of voluntary and involuntary exposure to cigarette smoke.

METHODS

Urine samples from 118 Japanese smokers and 117 non-smokers were analyzed using gas chromatography-mass spectrometry. Voluntary and involuntary smoking status was self-reported and workplace smoking restrictions were objectively evaluated.

RESULTS

The integrated sum of all concentrations showed 2.2- and 2.4-fold higher total levels (free and glucuronide) of nicotine and cotinine relative to the free levels. Median (quartiles) of total nicotine and cotinine were 1635 (2222) and 3948 (3512) ng/mL in smokers, and 3.5 (5.3) and 2.8 (4.2) ng/mL in non-smokers. Concentrations of urinary nicotine were higher than those of cotinine in 21 % of smokers and in 54 % of non-smokers. Nicotine and cotinine levels were significantly associated with a smoking habit, as well as being significantly associated with the workplace and home environments of non-smokers.

CONCLUSIONS

The present method can monitor voluntary and involuntary exposure to tobacco smoke. Measuring total urinary nicotine levels might be useful for analyzing exposure to cigarette smoke among non-smokers.

Fast and sample cleanup-free measurement of nicotine and cotinine by stable isotope dilution ultra-performance liquid chromatography-tandem mass spectrometry

We developed a stable isotope dilution ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry assay to measure nicotine and cotinine, the major oxidative and pharmacologically less active metabolite of nicotine, in human urine. A simple dilution step was used as sample preparation and the measurement of nicotine and cotinine was performed during a 1.5-min run-time using nicotine-D₄ and cotinine-D₄ as internal standards. Multiple calibration curves for the analysis of both nicotine and cotinine exhibited a consistent excellent linearity and reproducibility in the range of 5-35,000 μg/L (r>0.999). Limits of Detection were 0.7 μg/L for nicotine and 0.4 μg/L for cotinine, and Lower Limits of Quantification were 1.7 μg/L for nicotine and 1.1 μg/L for cotinine. The intraassay coefficients of variation (CVs) for nicotine and cotinine were <4% and <2%, respectively, the interassay CVs were <6% for nicotine and <4% for cotinine. The inaccuracy was <6% for both substances. The mean recovery was 103.2% (range 96.8-105.1%) for nicotine and 97.4% (range 94.3-99.2%) for cotinine. A method comparison showed that the values of nicotine metabolites in human urine samples (n=98) measured by a commercially available chemiluminescent immunoassay tested on analyzer IMMULITE 2000 were much higher than the cotinine concentration in the same urine samples measured by our UPLC-MS/MS assay. The Passing-Bablok regression line was: immunoassay=4.62 (UPLC-MS/MS)+3.64 [μg/L]; r=0.75. This robust, sensitive and interference-free UPLC-MS/MS assay permits rapid and accurate determination of nicotine and cotinine in human urine.

Self-reported tobacco smoke exposure and plasma cotinine levels during pregnancy--a validation study in Northern Japan

Maternal smoking is a critical public health concern requiring the establishment of its prevalence rate and clinical impact. Maternal self-reported information of tobacco smoke exposure requires validation using accurate biochemical analysis. This study examined the association between self-reported exposure to tobacco smoke and plasma cotinine level in Japanese pregnant women. We collected information about smoking and secondhand smoke (SHS) exposure during pregnancy from 5128 pregnant women in a prospective cohort design, and analyzed biochemically maternal blood samples using the enzyme-linked immunosorbent assay (ELISA) technique. Based on self-reports, the subjects were classified into three groups: 650 smokers, 728 ex-smokers and 3750 non-smokers. Using the receiver operating characteristic (ROC) curve, plasma cotinine cut-off value of 11.48 ng/mL was established for separating smokers from non-smokers, resulting in a smoking prevalence of 14%. A cotinine cut-off value of 0.21 ng/mL for discriminating exposed and unexposed nonsmokers resulted in a 63% prevalence of exposure to tobacco smoke among nonsmokers. Cotinine biomarker analysis proved accurate in validating self-reported smoking information in the subjects. Lower validity of SHS exposure suggests a need to confirm questionnaire information with biochemical analysis.